Definition of scruple:
a weight of twenty grains; the third part of a dram; hence, a very small quantity; a particle
"I will not bate thee a scruple. Shak."
to be reluctant or to hesitate, as regards an action, on account of considerations of conscience or expedience; to regard with suspicion; to hesitate at; to question
"others long before them ... scrupled more the books of hereties than of gentiles. -Milton."